Means for controlling hydraulic cylinders and like actuators



L. PERAS Filed may 27, 1960 Nov. 19, 1963 MEANS FOR CONTROLLING HYDRAULIC CYLINDERS AND LIKE ACTUATORS Fig- L+ United States Patent O M 3,111,062 MEANS FOR CONTROLLING HYDRAULIC CYLINDERS AND LIKE ACTUATORS Lucien Pras, Billancourt, France, assignor to Regie Nationale des Usines Renault, Billancourt, France, French works Filed May 27, 1960, Ser. No. 32,155 Claims priority, application France June 3, 1959 3 Claims. (Cl. 92-13) This invention relates in general to hydraulic cylinders and -like actuators and has specific reference to control means therefor.

More particularly, it is an essential object of the present invention to provide improved control means for hydraulic cylinders and like .actuators which are characterized in that they provide:

(l) A fast approach-stroke of the piston;

(2) The stoppage of the piston and an efficient damping out of the kinetic energy of the movable assembly thereof at a distance adjustable from its point of application;

(3) The application of a substantial 'effort 4to the piston rod with a relatively short stroke thereof.

According to the essential feature characterizing this invention the apparatus consists of a main hydraulic cylinder associated with an auxiliary or secondary hydraulic cylinder, said main hydraulic cylinder comprising the operating rod and the members operating under load whereas said auxiliary hydraulic cylinder determines the approach stroke of said operating rod by transmitting to this end the thrust exerted through a low-pressure fluid to one face of a free piston adapted to engage the end rod of the movable assembly of said main cylinder which is opposite to said operating rod, the movement of said free piston being controlled directly or indirectly by the compression of a spring and by a stop, the movable assembly of said main cylinder carrying two pistons actuated the one by a high-pressure fluid for operating the apparatus under 'load and the other by a low-pressure fluid for quickly returning the operating rod to its initial position. This arrangement is relatively simple and comprises means for varying with precision the value of the fast approach stroke. (It is advantageously applicable to those cases where a rapid approach stroke is necessary and where it is desired to reduce to Zero the kinetic energy of the movable assembly before applying the actuating force, so that the latter will be applied Without any shock between the cylinder rod and the part, member or other element to be acted upon by this rod.

The device of this invention is applicable in many fields, notably to the control of machine-tools and resistance welding machine, especially in the case of delicate welding operations to be carried out on fragile bosses formed on thin sheet metal parts.

With the foregoing and other objects in View, the invention resides in the novel arrangement and combination of parts and in the ldetails of construction hereinafter described and claimed, it being understood that changes in the precise embodiment of the invention herein disclosed may be made within the scope of what is claimed without departing from the spirit of the invention.

Other objects and ladvantages will become apparent from the following description taken in conjunction with the accompanying drawing in which:

FIGURE l is an axial diagrammatic section of a hydraulic cylinder arrangement constructed according to the teachings of this invention, the operating rod being retracted;

FIGURE 2 is a similar View of the same apparatus, wherein the operating rod has nearly completed its approach stroke;

3,1 1 1,062 Patented Nov. 19, 1963 FIGURE 3 is a View similar to FIGS. 1 and 2 but sho-wing Ithe apparatus vduring its operation under load, and

FIGURE 4 illustrates a modified embodiment of the apparatus, wherein the fast-approach motion is controlled by mechanical means.

As will be seen from FIG. :1, the movable assembly of the hydraulic cylinder comprises an operating rod 1 having two superposed pistons y2, 3; the lower or outer end 4 of the operating rod 1 is adapted to engage a piece, niember or other element 4S and its upper end 6 engages the free piston 7 of an auxiliary or secondary hydraulic cylinder 8. The lower chamber of this auxiliary cylinder 8 contains a liquid, for `example lo-il, rand is connected through a pipe 9 to another cylinder 10i in which a piston .11 is slidably fitted; this piston 11 lis constantly urged toward the fluid-filled chamber `of cylinder 10 by a compression spring 13. A threaded rod. -12 is provided in the oppos-ite end of the cylinder 1) for adjustably limiting the upward stroke of piston 11 in this cylinder. Pipe lines 14, 15 and 16 are provided Ifor supplying fluid unde-r pressure [to pistons 3, 2 and 7, respectively.

This device 'operates as follows:

I. Fluid under pressure lis directed into the pipe line 16, so that piston '7 moves downwards and drives oil into the pipe 9 to move the piston 11 upwards against the resistance of lthe compression spring `13. This movement is stopped when the piston 11 engages the threaded rod 12. During this movement the operating rod 4 has moved downwards to complete the fast-approach stroke.

fII. When the loperating lrod 4 is stopped, fluid under pressure is introduced into the line 14 (FIG. 2) and th-us a force is applied to the operating rod.

Ill. The permanent supply of fluid under pressure to the line 15 causes the rod and piston assembly to rnove upwards when the high-pressure feed and the delivery of fluid through line 16' :are discontinued.

In this case, as shown in FIG. 4, the apparatus does not require an external cylinder 10 as in FIG. l, but a chamber 1'8 of which the end walls act as limit stops to a disc 2i) carried by the rod 17 rigid with the cylinder.

The actuating fluid (which may be compressed air) is injected through a pipe 16, the function of yorifice 9 consisting in equalizing the pressure existing in the chamber 19 with the external pressure. Except yfor 'these differences, the `operation of the apparatus is Ithe same as that of the embodiment described hereinbefore.

Although the present invention has been described in conjunction with preferred embodiments, itis to be understood that modifications and yvariations may be resorted to without departing rfrom the spirit and scope of the invention, as those skilled in the art will readily understand. Such modifications and variations `are considered to be within the purview and scope of the invention and appended claims.

I claim:

1. Device for controlling hydraulic actuators comprising a single body, a first cylinder in the body, Ia first piston in said cylinder having one end smaller in diameter than the other, an operating rod connected to the large end of the first piston, said lrod projecting through the bottom of the first cylinder, a secondary cylinder disposed in said body, a seconda-ry piston in said secondary cylinder, an outer end rod engaging the secondary piston and the smaller end of the first piston, a chamber formed above the secondary piston and an orifice for introducing actuating fluid to said chamber `for insuring a rapid approach stroke `of the iirst piston, the portion of the cylinder below lthe first piston constituting a low pressure chamber, an orifice in said low pressure chamber for introducing fluid under low pressure for insuring the return of the operating rod, the portion of the rst cylinder above the smaller end of the piston constituting a high pressure chamber, an orce in said chamber for introducing uid vunder high pressure for insuring the slow operation of the operating rod.

2. Device according to lclaim 1, wherein said secondary piston is a tree piston, the advance of said `free piston being regulated by means of an auxiliary cylinder containing a second free piston, an adjustable stop mounted in said auxiliary cylinder to limit the stroke of the second free piston, spring means mounted in said auxiliary cylinlder and acting on said second free piston to compress a fluid which ris in communication with the portion of the chamber of the secondary cylinder that receives said outer end rod.

3. Device according to claim l, wherein said secondary piston is a -free piston, means located in said secondary cylinder for Ilimiting the travel of said free piston, the portion of said secondary cylinder that contains said outer end rod being in communication with the atmosphere.

References Cited in the file of this patent UNITED STATES PATENTS 1,787,328 Schott-1er Dec. 30, 1930 2,095,820 l Lenz Oct. 12, 1937 2,648,312 Tucker et al Apr. 1l, v1953 2,716,395 Pettigrew et al. Aug. 30, 1955 

1. DEVICE FOR CONTROLLING HYDRAULIC ACTUATORS COMPRISING A SINGLE BODY, A FIRST CYLINDER IN THE BODY, A FIRST PISTON IN SAID CYLINDER HAVING ONE END SMALLER IN DIAMETER THAN THE OTHER, AN OPERATING ROD CONNECTED TO THE LARGE END OF THE FIRST PISTON, SAID ROD PROJECTING THROUGH THE BOTTOM OF THE FIRST CYLINDER, A SECONDARY CYLINDER DISPOSED IN SAID BODY, A SECONDARY PISTON IN SAID SECONDARY CYLINDER, AN OUTER END ROD ENGAGING THE SECONDARY PISTON AND THE SMALLER END OF THE FIRST PISTON, A CHAMBER FORMED ABOVE THE SECONDARY PISTON AND AN ORIFICE FOR INTRODUCING ACTUATING FLUID TO SAID CHAMBER FOR INSURING A RAPID APPROACH STROKE OF THE FIRST PISTON, THE PORTION OF THE CYLINDER BELOW THE FIRST PISTON CONSTITUTING A LOW PRESSURE CHAMBER, AN ORIFICE IN SAID LOW PRESSURE CHAMBER FOR INTRODUCING FLUID UNDER LOW PRESSURE FOR INSURING THE RETURN OF THE OPERATING ROD, THE PORTION OF THE FIRST CYLINDER ABOVE THE SMALLER END OF THE PISTON CONSTITUTING A HIGH PRESSURE CHAMBER, AN ORIFICE IN SAID CHAMBER FOR INTRODUCING FLUID UNDER HIGH PRESSURE FOR INSURING THE SLOW OPERATION OF THE OPERATING ROD. 